Punch



I Dec.22,1931'. I H. c. LEE I 1,837,451

Filed Dec. 19, 1930 2 Sheets-Sheet l Dec. 22, 1931: H. c. LEE 1,837,451

' runca- I Filed Dec. 19, 1,930 2 Sheets-Sheet 2 Patented Dec. 22 1931 UNITED STATES PATENT OFFICE HERMAN G. LEE, MADISON, WISCONSIN, ASSIGNOR TO G. F. BURGESS LABORATORIES,

' INCL, OF MADISON, WISCONSIN, A CORPORATION OF DELAWARE PUNCH Application filed December 19,1930. Serial No. 508,544.

This invention relates to improvements in punches, and more particularly to a punch adapted to pierce or perforate thin sheet metal and especially metal foil constituting 1 a facing material for pourous sound-absorbing material.

It is the object of the invention to provide a. piercing punch which will not shear and remove the metal at the perforation but will in deform it in a peculiarly beneficial manner so as to accomplish an interlocking of the contiguous surfaces of the porous sound-absorbing material and of the sheet metal facing. In this way the necessity for using an adhesive is obviated.

The invention will be described in connection with the accompanying drawings, in which:

Fig. 1 is a sectional view of a sound-absorbing pad faced with thin sheet metal which has been pierced by means of my improved punch, shown in the position, it occupies when applied to a ceiling;

Fig. 2 is an enlarged cross-sectional view of said sound-absorbing pad and sheet metal facing at one of the perforations;

Fig. 3 is a perspective view of my improved punch; V

Figs. 4-7 illustrate the deformation of the sheet metal as the punch penetrates progressively to its maximum depth in the sound absorbing material.

Fig. 8 is a perspective view of a modified form of m improved punch.

Fi 1 il ustrates a simple form of soundabsor ing construction with which'my improved punch is adapted to be used. This construction is described and claimed in copending patent application of Charles F.

0 Burgess, Serial No. 503,543, filed Dec. 19, 1930. Briefly sound-absorbing material 10 is faced with thin perforated metal 11, which is preferably metal foil. Metal sheet 11 has perforations "12 punched therein in such manner that the metal facing is locked to the sound-absorbing material, as hereinafter de- "scribed. The'size and distributon of the perforations 12 ma hear such relation to the ayerage of the en h of the sound waves striking the "metal aced pad as to result in the absorption of a very high percentage of the sound as described in U. S. Patent 1,726,500, granted August 27, 1929 to R. F. Norris.

The perforating operation is performed preferably in the following manner. The pad 10 of porous material, which is usually of fibrous structure, is placed upon a support with the surface uppermost which it is desired to face with metal. The metal sheet is 0 then placed upon the pad and may be glued thereto if desired. The piercing operation is then performed by means of a punch such as shown in Fig. 3. The design of the punch is such that none of the metal around the opening is sheared off, and, furthermore, the material at the perforations is not torn and displaced in irregular fashion but is pierced, cut and bent to the shape of part of the punch and then bent back into the abutting material 7 of the pad in the form of tangs or hooks 13 of regular predetermined shapes In other words, the shape and disposition of the metal removed from the perforations is controlled. An opening 14 is left in the pad extending inwardly beyond the ends of the tangs.

The punch comprises successive portions 15, 16, 17 and 18. The end is a pyramidshaped point 18. The number of sides of the pyramid and the widths of the diiferent so sides at their bases may be varied as desired, depending upon the character of the perforations and the number of tangs it is desired to have. The intersections between adjacent sides should be sharply angular in order that there may be a clear separation of the metal into as many tangs as there are sides of the pyramid-shaped point.

Continuing rearwardly from the base of the pyramid-shaped point is intermediate shank 17 which has the same number of sides as does point 18. The sides are preferably substantially parallel to the longitudinal axis of the punch. There should, however, be

a slight forward taper upon shank 17. to facilitate removal of the punch after a perforation has been made. It has been found that unless the shank has a slight taper it will pull and displace the tangsduring removal of the punch. The taper may need to be only a few ten-thousandths of an inch but this is a matter in which I do not wish to restrict myself since itvaries with the size of the punch and the character of the material which is being perforated. The length of shank 17 may be varied to some extent but it should be at least equal to one-half its greatest thickness at its bottom when in the position shown, indicated by line A in Fi s 3. Continuing rearwardly from shank 1 is a diverging frustum-pyramid-shaped section 16. The length and angularity of section 16 may be'varied to alter the character of the perforations as will be explained hereinafter.

Continuingrearwardlyfromfrustum-pyramid-shaped section 16 is shank which may be adapted to be mounted in any desired manner. The punch may be operated singly or in groups. In either case the punch or the pad preferably, is movable along guideways to permit accurate spacing and location of the perforations. A plurality of punches 'may be mounted rigidly upon a movable the metal sheet in a uniform plane.

frame in such a manner that an entire pad or so-called title may be punched in a single operation.

In order that the invention be understood thoroughly, a punching operation will be described in detail. In Fig. 4 the punch is shown as having pierced metal sheet 11 and being imbedded to the base of the pyramidshaped point 18. The sharply angular edges of the point have cut the metal at the perforation along definite lines to form tangs 13 of predetermined shape. Said tangs 13 are depressed to a position parallel and adjacent the surfaces of point 18. It is apparent that if the point 18 is too blunt, excessive pressure is required to pierce the metal sheet and irregular tearing may occur. In the case of materials which do not possess stiifness, such as metal foil, the surface plane of the unpunched areas probably will be more or less irregular if a blunt point is used since the porous material 10 is usually too saft to hold Where the metal sheet is exposed to view, as it usually is, irregularities of such character are objectionable since the light reflection is nonuniform.-

Fig. 5 shows the punch .after it has penetrated to,the base of shank 17. The tangs 13 have been pressed to each" side. into positions substantially perpendicular to the surface. It is apparent that the shank 17 preferably should be as long as tangs 13 so that the latter are pressed perpendicularly to the sides throughout their entire length. Since the punch separates the metal atthe center of the perforation, the length of shank 17 should be equal to at least one-half its greatest thickness at its top, in the position shown.

Fig. 6 shows the punch after it has penetrated to the base of diverging pyramidshaped section 16. The sharply angular edges of section 16 have cut additional metal 19 along the lines of separation of tangs 13. The additional metal, which has become the base portions of tangs 13, is shown as being depressed downwardly at an angle to the sur face equal to the angle which the surfaces of section 16 makes, with the surface of the metal sheet. The end portions of tangs l3 retain their angular relation with base portions 19 to a greater or lesser extent depending upon the stiffness of the sheet material and the hardness of porous material 10. The depth to which the punch is caused to penetrate may be varied to suit the circumstances but for the constructions with which this invention is primarily concerned, the depth shown in Fig. 6 is usually sufficient, since the base and end portions of tangs 13 are at a sufficient angle to one another to interlock the metal sheet and the sound-absorbing material and, at the same time, the base portions impart a desirable light reflection which assists in rendering the perforations unnoticeable when the construction is installed upon walls and ceilings, In other Words the interlocking action is obtained without apparent increase in the size of the perforations. It is obvious that the angle of depression of metal portions 19 may be varied by changing the angle of divergence of section 16 of the punch.

Fig. 7 shows the punch after shank 15 has penetrated appreciably into the perforation. The base portions 19 of the tangs are now pressed to the sides to position them substantially perpendicular to the surface. The end portions are pressed further into the soundabsorbing material and the interlocking action may be desirable with certain combinations of sheet metal and sound-absorbing material, in which case the over-all size of the punch may be decreased to prevent the perforations from being objectionably large. The angularity of diverging section l6w1ll again affect the pressure required to cause penetration of the punch and may be varied as is found most suitable for the type of sheet material which is being used. Shank 15 should also have a slight forward taper for the same reasons mentioned in connection with shank 17. Fig. 8 shows a punch which has an additional diverging frustum-pyramid shaped section 20, which may be used if it is desired to increase the hOOkiIlg action of the tangs.

Although the punch in the forms described is adapted particularly for use in the manu' facture of sound absorbing construction, it is useful also in other classes of service.

I claim: 1. A piercing punch comprising a pyramidal point, an intermediate shank continuing from the base of said point, a frustumpyramidal section diverging from the base of said intermediate shank, and a shank continumg from the base of said frustum-pyramidal section.

2. A'piercing punch comprising a tapered polygonal point, a substantially longitudinal shank extending from the base of said point, a tapered polygonal section diverging from i the base of said shank and a second shank extending longitudinally from the base of said diverging section.

- 3. piercing punch comprising a sharply angular pointed pyramid, an intermediate shank continuing from the base of said pyramid, a frustum-pyramidal section diverging from the base of said intermediate shank, and

a shank continuing from the base of said frustum-pyramidal section.

a. A punch for piercing sheet metal comprising a polnt in the form of a pyramid, the

intersections of the triangular faces of the pyramid beingsharply angular, a substantially longitudinal intermediate shank continuing from the base of said pyramid, a frustum-pyramidal section diverging from the base of said intermediate shank, and asecond shank continuing longitudinally from the base of said diverging section.

5. A punch for piercing sheet metal comprising a point in the form of a sharply pointed pyramid, a longitudinalintermediate shank continuing from the base of said pyramid, the base of said shank being slightly larger than the t0'p,'a frustum-pyramidal section diverging from the base ofsaid intermediate shank, and a second shank continuing longitudinally from the base of said diverging section.

6. A-punch for piercing sheet metal comprising a pointed pyramid, the intersections between the sides of said pyramid being sharply angular, a longitudinal shank extending from the base of said pyramid, said shank having a length equal to at least onehalf its greatest thickness at its base, the thickness of said shank being slightly greater at the base than at the top, a diver 'ng frustum pyramidal section. extending om the base of said shank, and a second shank extending from the base ofsaid frustum-pyramidal section.

In testimony whereof, I have subscribed my name.

HERMAN 0. LEE. 

